Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W = map(int,input().split())
s = []
black = 0
for i in range(H):
    l = list(input())
    for j in range(W):
        if l[j] == "#":
            black += 1
    s.append(l)
white = H*W-black
from collections import deque
q = deque([(0,0,0)])
s[0][0] = "#"
while q:
    x,y,cnt = q.popleft()
    for dx,dy in [(0,1),(0,-1),(1,0),(-1,0)]:
        nx,ny = x+dx,y+dy
        if 0<=nx<H and 0<=ny<W and s[nx][ny] != "#":
            if nx == H-1 and ny == W-1:
                print(white-cnt-2)
                exit(0)
            s[nx][ny] = "#"
            q.append((nx,ny,cnt+1))
print(-1)